I have both a gas type with 2500 psi(do not use 0 degree nozle it will bore holes and do damage)and a steam cleaner with 1500 psi. If you are going to rent a unit I would rent a steam cleaner. The job goes faster and you dont need chemicals. They are expensive to purchase but comparable to others as to rental cost. They outperform pressure washers hands down. They will make shorter work of a nasty job and you will be pleased with your results. More pressure may mean more damage.
